Starting on the 3rd row, inc at the beg and end of every row until you have 104 sts. Then inc on every other row (following alt rows) until there's 122 sts. When you inc every other row, that's usually done on the RS rows. So if you get to 104 sts on a knit row, then work the purl row and inc again on the knit row which would start the every other row iinc pattern.